Field of the Invention
The invention relates to an analog-to-digital converter (ADC), and more particularly to an ADC that uses dynamic biasing techniques.
Description of the Related Art
Currently, analog-to-digital converter (ADCs) are widely used in a variety of applications, such as medical systems, audio systems, test and measurement equipment, communication systems, and image and video systems, etc. The most common ADC construction comprises flash ADCs, pipeline ADCs and successive approximation register (SAR) ADCs. Although the flash ADC and the pipeline ADC are faster than the SAR ADC, their power consumption is also larger, and are not suitable for many systems with limited power supply, such as portable devices.
Types of the SAR ADCs comprise resistor string SAR ADCs which use resistive digital to analog converters (RDACs), capacitor array SAR ADCs which use capacitive digital to analog converters (CDACs), and resistor-capacitor (R-C) hybrid SAR ADCs which use hybrid DACs (i.e. C+R DACs). In general, the capacitor array SAR ADC has better linearity than the resistor string SAR ADC. Furthermore, the R-C hybrid SAR ADC is often used to reduce area due to lengthy resistor strings or bulky capacitor arrays when physically laid out. However, large capacitance is required due to limitations in semiconductor processes, causing larger area and increasing power consumption.
Therefore, it is desired to decrease power consumption for the SAR ADCs.